1. Field of the Invention
The present invention relates to fully or partially automated vehicular transmission systems having at least one mode of operation wherein shifts from a currently engaged gear ratio into an automatically selected target gear ratio are automatically initiated at a selected engine speed for a given set of vehicle operating parameters. In particular, the present invention relates to fully or partially automated transmission systems of the above-described type wherein the vehicle driver can manually modify, within limits, the engine speeds, often referred to as shift points or shift profiles, at which shifts will be automatically initiated in the automatic shift initiation mode.
2. Description of the Prior Art
Fully and partially automated vehicular transmission systems having at least one automatic shift initiation mode wherein shifts from a currently engaged gear ratio into a selected target gear ratio are automatically initiated at a selected engine speed for a given set of vehicle operating conditions are well known in the prior art. Examples of such transmission may be seen by reference to U.S. Pat. Nos. 4,361,060; 4,430,911; 4,648,290; 4,722,248; 5,053,961; 5,053,962 and 5,109,721, the disclosures of all of which are incorporated herein by reference.
In such prior art automated transmission systems, it is known to define a standard or default set of conditions, including engine speed, or a related parameter usually called shift points and/or shift profiles, at which, in the automatic shift implementation mode, and in the absence of preset conditions, a shift will be automatically implemented. It is also known to sense for the presence of such preset conditions, and to automatically modify the shift points/shift profiles by increasing or decreasing the engine speeds at shifts are automatically implemented in response to sensing the presence of such conditions. By way of example, in response to overtravel depression of the throttle pedal (i.e. "kick down"), upshifts may be delayed by increasing the engine speeds at which upshifts are initiated. For another example, to prevent "hunting", for a period of time after a downshift, the engine speeds at which upshifts are initiated may be increased and/or for a period of time after an upshift, the engine speeds at which downshifts are initiated may be decreased.
Examples of such automatic shift point/shift profile modification may be seen by reference to above-mentioned U.S. Pat. No. 4,361,060, and to U.S. Pat. Nos. 4,551,802; 4,569,255 and 4,852,006, the disclosures of which are incorporated herein by reference.
While the prior art fully or partially automated transmission systems did incorporate control strategies for automatically adjusting automatic shift initiation mode shift points in response to sensing the occurrence or presence of certain preset conditions, such systems are not totally satisfactory as such systems, in the automatic shift initiation mode of operation, do not allow the vehicle driver to manually temporarily modify the shift points, within limits, to achieve a then desired vehicle performance.